1. Field of the Invention
The present invention relates to ceramics and more particularly to methods for joining ceramic components.
2. Description of the Related Art
Advanced ceramics and fiber-reinforced ceramic matrix composites with characteristics such as high strength, toughness, good thermal conductivity, thermal shock resistance, and oxidation resistance are needed for many applications. The properties of many ceramic materials, such as hardness, stiffness, heat-resistance, corrosion resistance, low density, and low cost, make these materials highly desirable for many applications, including aeronautical, automotive, military, communications, medical, consumer, and computer applications, to name just a few.
Nevertheless, engineering designs for many applications require fabricating parts with relatively complex shapes and geometries. Many of these shapes may be quite expensive and in some cases impossible to manufacture using conventional ceramic fabrication techniques. For example, as illustrated in FIG. 1, a simple U-shaped tube 100 may be very difficult to produce using conventional ceramic fabrication techniques, such as slip casting, tape casting, injection molding, dry pressing, or the like.
In many cases, it may be more cost-effective to produce complex shapes by joining simpler geometrical shapes together. For example, as illustrated in FIG. 2, it may be more cost-effective to produce the U-shaped tube 100 illustrated in FIG. 1 by joining together multiple simpler components 200a-d, each of which may be more easily fabricated using conventional ceramic fabrication techniques. Accordingly, the ability to join multiple ceramic components together is an important to the utilization of advanced ceramics and fiber-reinforced composite components in many applications.
Currently, ceramic components may be joined together using various conventional organic adhesives. Many of these adhesives, however, may combust and degrade when subjected to temperatures exceeding 200° C. Other inorganic ceramic binders have been developed that can withstand temperatures of 1600° C. or more. These binders typically combine an inorganic binding compound, such alkali silicates or metal phosphates, with ceramic powders, such as powders of alumina, silica, magnesia, or zirconia. Many of these binders, however, do not provide the strength needed for many applications. Other binders may shrink more than desired or exhibit different thermomechanical properties (e.g., coefficient of thermal expansion (CTE)) than the materials they bind together. Other binder types degrade in strength at higher temperatures.
In view of the foregoing, what is needed is an improved method for joining ceramic components that exhibits acceptable strength, environmental stability, and thermomechanical properties that are stable at high temperatures. Ideally, the method would provide a bond with properties comparable to those of the material or materials it binds together. Further needed is a method to create a bond that will begin bonding at room temperature, exhibit minimal shrinkage, and increase in strength as it is exposed to higher temperatures.